Knowledge of the Ancients. 269 
from water, by freezing the latter, appears to 
have been not unknown to the ancients. Pro¬ 
bably, this is what was meant by Hippocrates, 
when he fays, tf that the clear, light, and fweet 
parts of the water, are difiipated by freezing;** 
an opinion which Ariftotle feems to have adopted, 
probably from this fource. 
Aulus Gellius* explains this paffage of Ari¬ 
ftotle, as if the air was prefied, as it were, from 
water, by its concretion ; and Macrobius f ex- 
prefies the fame, in terms more plain and dif- 
tinfir, and feems to fay, that it was necefiary for 
water to part with its air, in order to its con¬ 
gelation. 
VII. It is often imagined, that the fa£V, Of water 
rifing to its level in pipes, was a modern dif- 
Aat ts airt zasi y.^varciWa v v^ara. tya.v'hx tcrriv ; oti wa/roj 
Vitccroc 'rcvfpvy.trt ro he7r%Ta,T0v xai xutyototTov 
Arift, Meteor. 
* Quoniam cum aqua frigore aeris duratur, et coif, 
necefle eft fieri evaporationem, et quandam quafi auram 
tenuillimam exprimi ex ea et emanare : id autem, inquit, 
in ealeviftimum eft quod evaporatur. 
Aul. Gell. No£t. Attic. IX. 5. 
f Omnis aqua, inquit, habet in fe Aeris tenuiflimi por- 
tionem, qua falutaris eft : habetque terream faecem, qua eft 
corpulenta poll terram. Cum ergo Aeris frigore et gclu 
coadta calefcit, necefle eft per evaporationem velut ex¬ 
primi ex ilia Auram tenuiflimam, qua difcedente conveniat 
in coagulum. 
Macrob. Saturn. L. VII. C. 12. 
covery; 
